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Sebastian Vettel says he and Red Bull have to make the right calls this weekend

World Champion says weather conditions will be key to Brazil success

By Mike Wise at Interlagos

Last Updated: 22/11/13 9:03pm

The World Champion is looking to claim a record-equalling ninth straight victory on Sunday but was knocked off his P2 perch for the first time since Korea after Mercedes' Nico Rosberg topped both sessions.

Both practice sessions were held in changeable conditions typical of Interlagos, with rain falling through most of the second session.

More rain is forecast for qualifying and perhaps the race as well, with Vettel knowing that a certain degree of opportunism will probably be needed if he's to chalk up win number 13 of 2013.

"Yes. Obviously you could tell that people didn't run a lot this afternoon simply because they want to save their tyres," he said afterwards.

"It's a bit of a shame for the people out in the grandstands when it's like this. But on Sunday and Saturday you need to have the tyres and you need to make the right decisions.

"It's good to get a bit of a baseline in these conditions but you have to be sharp tomorrow and Sunday.

Vettel, who won his third title in similar conditions 12 months ago after recovering from a lap-one collision, added: "It's a long way through the race, especially around here. It's 70 laps to the chequered flag and we know that Sao Paulo is crazy.

"You need to keep your eyes open and make the right calls."

Team-mate Mark Webber, who finished third fastest, said it was important to gauge the 'crossover' between the full wet and intermediate tyre.

"It's about understanding the tyres in both conditions; we need to understand the full wet to the inter and also we did quite a few laps on one set of tyres, the inters," said the Australian, who will retire from F1 after Sunday's race.

"It was a productive day in preparation for tomorrow because we expect still some wet track conditions and we'll go from there.

"Obviously, you've also got to understand the inter on a long-ish run and on a short run and also save tyres.

"A bit of a testing day for the teams but we got what we could out of the day."